Hope you get to the bottom of this, OP.
Years ago, before political correctness was a common concept a friend of mine was accused of racism. We were at school and walked into a classroom which was stuffy. My friend said, "ooh, it stinks in here!"
For whatever reason, someone else understood that to mean "Oh, there are a number of non-white pupils in here and that is why it stinks in here" and made a complaint about her.
Fortunately the school were, for all their other faults, keen to hear both sides of the story and witnesses were called. It could have been much worse.
If it is the case that the incident pivots wholly around your daughter describing another child by their skin colour, although it was perhaps, in retrospect misguided, it is not racist.
I have friends of different ethnicities and when I have asked them how they like to be described, in such scenarious, then they'll say "The black one"/"the chinese-looking one"/"The indian one". One of my friends has mobility problems and refers to herself as "a fat cripple." It isn't a term I would use at all in describing her, but she says that's what she is.
At our school we have a couple of mums who share the same name. Both are tall and willowy, both have two children (of the same genders, in the same year groups). If describing them to someone they are either, "Jane, Freddie's/Polly's mum" or "Jane, Toby's/Anna's mum." If that doesn't help then they are "White Jane" and "Black Jane". I'm known as "the crazy short one with pink hair".